


Deriving

by haekass



Series: Fucking Calculus [1]
Category: Super Junior
Genre: M/M, maths warning, no seriously this is actual maths
Language: English
Status: Completed
Published: 2012-06-29
Updated: 2012-06-29
Packaged: 2020-05-31 10:35:26
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,901
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19424230
Author URL: https://archiveofourown.org/users/haekass/pseuds/haekass
Summary: Donghae hates calculus. Right up until Hyukjae shows him a new way to think about derivatives.





	Deriving

“I just _do not get this_.”

A soft sigh. “I promise it's not that hard, Donghae.”

Donghae made a sound of frustration in the back of his throat. “That's easy for you to say, you were probably born knowing how to figure out calculus!”

Hyukjae rolled his eyes. “No, it took me a lot of hours studying this to finally get it,” he retorted, his voice sharp.

Donghae groaned and let his head fall onto his open calculus book. “Great, just great.” He bit his lower lip to prevent the tears of frustration from falling. He knew he wasn't the brightest crayon in the box when it came to higher level math, but he had to pass calculus in order to graduate. And he was trying to study for a test, but still not having much luck understanding derivatives. It was like once things got beyond the Power Rule, his brain just shut down, and panic would set in.

Hyukjae sighed and rubbed a comforting hand over his boyfriend's back. He did understand calculus, but he knew that Donghae understood things in a different way than what he did. It seemed that they just weren't looking at things the right way. He'd tried using the onion peeling analogy his professor had taught him, but Donghae had just cutely wrinkled his nose and said that he hated onions and the way the smell would linger on his hands after he peeled one. He looked at the problem they were trying to go over. It was fairly simple to Hyukjae, just applying the chain rule and remembering that the derivative of e to the x was e to the x.

He looked at Donghae, who was now pouting, and he wished they could hurry this up so he could make Donghae relax in the way only he could...

His widened for a second. It couldn't be that easy, could it...? He looked down at himself, mentally counting, and a little smirk tilted his lips. “Hey baby? I think I know something that will help.”

Donghae turned his head a little bit, knowing that tone of voice. He looked skeptically at his boyfriend. “What?” he grumped.

“Since you don't like peeling onions, I know something that you _do_ like peeling.”

Hyukjae watched Donghae sit up, a confused and frustrated look on his face. “Huh?”

He tapped the problem that they were working on. “Think of this problem as me, baby. I'm all bundled up in clothes and you want to get me naked.”

Donghae's brain almost shut down at the mention of the word 'naked' but he blinked and forced himself to untangle Hyukjae's sentence. But when he got it, a smile spread across his face. “I think I like where this is going.”

Hyukjae smiled at him, all gums and eye wrinkles. “I thought you would once you understood what I was trying to get at. So my socks are the cube, and the rest of my clothes are the e raised to the sine of t-half. What's the first thing to go in one move? You can't get my shirt and pants off at once, so that means...”

“Your socks.”

“So ignore everything inside the parenthesis, it's not important right now, just derive my socks off.”

Donghae snorted a laugh, and wrote down the first part of the derivation. He knew the power rule, so he brought down the exponent, then wrote out the rest of the equation, and squared it. He put in a multiplication symbol, then looked expectantly at Hyukjae, who smiled at him and tossed his socks towards the laundry hamper.

“Now I'm left in my shirt, my pants, and my boxers. My shirt is the e, my pants are the sine, and my boxers is standing for the t-half. You still only have one move, so what's next?”

Donghae looked at Hyukjae. “Your... shirt?”

The brilliant smile was the indication that he got the next step right. “Now here's the trick, baby. Ignore my pants and boxers, it's not important at the moment. You just want to get my shirt off. What's the derivative of e to the x?”

Donghae blinked. “Uh... Oh! Isn't it that a special one? E to the x, right?”

“Right! So even though it looks the same, it's the derivative.”

Donghae smiled. “Which means your shirt comes off, right?”

Hyukjae laughed and pulled his shirt over his head, letting it drop to the floor next to him. “Now write it down.”

Donghae obediently wrote down _e raised to the sine of t-half_ and shifted slightly to ease the pressure his jeans were starting to put on his dick. “Next is your pants, I'm guessing?” he asked his voice a little rougher.

“I think you're starting to get it. Derive my pants off, baby. Ignore my boxers for now.”

Donghae's pencil moved swiftly over the paper, multiplying by the derivative of sine, which was cosine of t-half. He didn't even bother asking what the next step was. He had reached his light bulb moment and he multiplied the last part of the derivation, which since it was one half of t, turned into one half. Throwing down his pencil, he watched as Hyukjae's pants fell to the ground, followed quickly by the boxers Donghae was pretty sure belonged to him.

Hyukjae was already hard and Donghae had zero qualms about immediately dropping to his knees and almost immediately taking the entire length into his mouth at once.

“Oh fuck, _Donghae_ ,” Hyukjae moaned, and it was the balm his brain needed after several hours of calculus. Donghae moaned in return when Hyukjae's dick hit the back of his throat and he loved the startled gasp that left Hyukjae's mouth, smiling a little to himself.

Hyukjae gripped Donghae's hair, trying to keep his brain from melting and his body from releasing far too soon. Finally gaining _some_ control, he looked down and brushed his hand over Donghae's cheek. Their eyes met and Hyukjae smiled. “What do you want tonight, baby?”

With a last swirl of the tongue, Donghae managed to detach his mouth from Hyukjae's dick. He thought about it for a moment, considering. He much preferred having Hyukjae slamming into him, letting the searing pleasure break him apart, and he knew that Hyukjae really had no complaints if Donghae wanted to turn the tables on any given night, either. Who fucked who was almost a secondary consideration, the primary one being that both of them felt good. He quirked his lips.

“Do you have any dancing tomorrow?” He watched Hyukjae's pupils dilate even more, the brown of his eyes becoming black, at the blatant insinuation in Donghae's voice.

“Nope,” Hyukjae replied easily. He marveled, not for the first time, how easily they shared dominance over the other. He was surprised though to hear that Donghae wanted to fuck him, half expecting Donghae to pout and demand to be taken care of after his battle with calculus.

They walked slowly backwards towards the bed, Donghae shedding – deriving – his own clothes along the way, before they landed in a heap on their shared bed. Their hands were everywhere on each other's bodies, trying to drive the pleasure upwards. Donghae almost snorted a laugh when he realized he was still thinking in math.

“What?” Hyukjae muttered.

“Never at you, Hyukkie,” Donghae murmured. “I was laughing when I realized I was still thinking in math terms.”

Hyukjae laughed. “How so?”

Donghae hummed and licked at a nipple, which obediently hardened. “Now that I've managed to derive you out of your clothes, I want to square your pleasure.”

“Ugh, that was cheesy. Why do I put up with you?”

“Because you love me,” Donghae immediately replied, reaching over Hyukjae and grabbing the lube and a condom. He felt a brush across his stomach and felt himself falter for a second. Hyukjae was trailing a couple of his fingers up and down his own cock, hedonistically teasing himself. He knew that Donghae loved that, loved watching Hyukjae tease himself until neither one of them could stand it. Their eyes met and held, the love shining deeply there.

Squirting some lube onto his fingers, Donghae's fingers briefly tangled with Hyukjae's before sliding lower, a slick finger teasing the tight ring of muscles for a long moment before sliding in, a long sigh coming from Hyukjae's mouth.

“Okay Hyukkie?”

Hyukjae smiled, not opening his eyes. “Yeah, I'm good. Keep going.”

So Donghae continued on, slipping another finger inside, gently stretching before trying to add a third finger, then stretching some more and adding a fourth. When Hyukjae's back arched and his hips started moving on their own against his fingers, Donghae knew that his lover was ready. Pulling his fingers out, he quickly rolled the condom on and made sure to cover it well with lube.

Hyukjae was watching him, his full lips parted and red, eyes almost black, a light blush staining his sharp cheeks. They smiled at each other before Donghae slowly pushed his way inside of Hyukjae, fighting the urge to go faster. He wanted to make this last, but he could feel the muscles tightening and relaxing, fluttering around his dick, and knew Hyukjae was pretty close to coming.

“Oh my God how in the hell did I forget how good you feel inside me, Donghae?” Hyukjae panted.

Donghae chuckled. “Because I love feeling you inside me and you love making me scream and claw at your back.”

“So why don't you make me scream and claw at yours?” Hyukjae teased, rolling his hips, both of them moaning at the sensation.

Pulling out, Donghae thrust back inside, setting a fast pace, satisfied when Hyukjae was meeting his every thrust with a liquid roll of his hips and groans of pleasure, groans that turned into near screams when Donghae shifted his angle slightly and was now hitting Hyukjae's prostate with every thrust in. He loved watching this, loved watching Hyukjae completely lose himself in sensation, and when the heat in his lower belly started to intensify, he reached between their sweaty bodies and palmed Hyukjae's cock with his hand.

Hyukjae's eyes shot open and a scream finally came from his throat as his blunt nails scraped down Donghae's back. It only took two more strokes before Hyukjae arched sharply, every muscle in his body tensing as he came, a throaty cry ripping free.

Seeing his normally composed lover coming apart was always such a visceral treat for Donghae, and with a hard thrust, his eyes rolled up as he finally came, his hips thrusting slowly as he savored his orgasm. Falling forward, he grimaced slightly at the wet feeling all over his stomach and heading up his chest, but was over it in a second when Hyukjae wrapped his arms around him.

“I think I like derivatives now...” Donghae mumbled.

Hyukjae chuckled wearily. “We'll discuss integrals in the morning.”

“What's that?” He asked as he pulled out of Hyukjae.

“It's like derivatives, but in reverse.”

Donghae made a face, but it morphed into a smile. “Thanks for explaining math to me, Hyukkie.”

Hyukjae smiled right back. “Think you'll pass your exam tomorrow?”

Donghae chuckled. “I know I will, but I'm probably going to be trying to hide my boner all day tomorrow from thinking about deriving all of our clothes off.”

“I can always help you with that problem, baby.”


End file.
